Accession Number : ADA306305

Title :   Effect of Low-Velocity Impact Damage on the Compressive Strength of Graphite-Epoxy Hat-Stiffened Panels.

Descriptive Note : Technical note,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER

Personal Author(s) : Rhodes, Marvin D. ; Williams, Jerry G. ; Starnes, James H., Jr

PDF Url : ADA306305

Report Date : APR 1977

Pagination or Media Count : 30

Abstract : An experimental investigation was conducted to determine the effect of low-velocity impact damage on the compressive strength of graphite-epoxy hat-stiffened panels. Fourteen panels, representative of minimum-mass designs for two compression load levels (0.53 MN/rn (3000 lbf/in.) and 1.58 MN/rn (9000 lbf/in.)), were tested. Eight panels were damaged by impact and the effect on compressive strength was evaluated by comparing the results with data for control panels. The impact tests consisted of firing 1.27-cm-diameter aluminum projectiles normal to the plane of the panel at a velocity of approximately 55 m/s to simulate impact damage from runway debris. The results of this investigation indicate that the extent of damage in the high-axial-stiffness region of both panel designs increased with the magnitude of applied axial load. The damage in panels designed for 0.53 MN/rn at a strain of 0.003h was local and the damaged panels were capable of carrying the design load. The panels designed for 1.58 MN/rn at a strain of 0.0080, however, failed due to impact damage at applied axial strains 50 to 58 percent of the design level. The existence of, and not necessarily the extent of, damage in the high-axial-stiffness region was the most significant factor in reducing panel strength. Limited damage that was not visually detectable reduced ultimate strength as much as extensive visible damage.

Descriptors :   *GRAPHITE EPOXY COMPOSITES, DEBRIS, PROJECTILES, IMPACT TESTS, PANELS, STIFFNESS, DAMAGE ASSESSMENT, ELASTIC PROPERTIES, STIFFENING, STRAIN(MECHANICS), IMPACT STRENGTH, LOW VELOCITY, ALUMINUM, BUCKLING, COMPRESSIVE STRENGTH, EPOXY RESINS, AXIAL LOADS.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE